97. The Five Genera of Powers of the Soul
Summary
Listen to Lecture
Subscribe in Podcast App | Download Transcript
Lecture Notes
Main Topics #
The Five Genera of Powers #
Thomas distinguishes five genera of powers:
- Vegetative (Living) Powers: Nutrition, growth, reproduction—found in all living things
- Sensitive Powers: Sensation—found in animals and humans
- Appetitive Powers: Desire—follows upon knowing powers
- Locomotive Powers: Motion from place to place—not in all animals
- Intellectual Powers: Understanding and reason—unique to humans
Three Souls vs. Five Powers #
While there are five genera of powers, only three souls are traditionally distinguished:
- Vegetative Soul (plant soul)
- Sensitive Soul (animal soul)
- Rational Soul (human soul)
The appetitive power does not constitute a separate soul because it always accompanies either sensation or understanding.
Four Grades of Life #
Despite five powers, only four grades of life exist:
- Plants: vegetative powers only
- Immobile animals: vegetative + sensitive powers
- Mobile animals: vegetative + sensitive + locomotive powers
- Humans: all powers including intellectual
The appetitive power does not create a separate grade because it necessarily accompanies knowing powers.
Key Arguments #
Why Five Powers but Only Three Souls? #
The distinction rests on how each soul rises above material nature:
- A soul is identified by its fundamental way of transcending matter, not by the number of powers
- Appetite always accompanies knowing, so it does not mark a distinct soul
- Locomotion, while distinctive, does not constitute a new soul because it depends on sensation or understanding for its operation
Why Five Powers but Only Four Grades of Life? #
Each grade of life represents what new operations become possible:
- Grade 1: Vegetative operations only
- Grade 2: Adds sensation (requires at least touch)
- Grade 3: Adds locomotion (movement from place to place)
- Grade 4: Adds intellection
Appetite is not a separate grade because:
- If something senses, it necessarily has some appetite (pleasure/pain response)
- If something understands, it necessarily has will
- Therefore appetite adds no new operational level
The Objection from Common Division #
Objection: Powers are sometimes divided into only three (vegetative, sensitive, rational) or two (active and passive). Why five?
Response:
- The threefold division refers to souls, not powers
- The twofold division (active/passive) is a different principle of division
- When formally distinguishing powers, the five-fold division is standard
The Objection from Desire as Universal #
Objection: Desire is common to all powers (even plants “desire” suitable conditions), so it should not be a separate genus.
Response:
- Desire as a common inclination is not the same as appetitive power proper
- Appetitive power proper always accompanies knowing powers (sensation or intellection)
- What is common to all should not be made a separate genus, but appetite proper is not truly common in this sense
Important Definitions #
Grades of Life #
Four distinct levels of living operations that build hierarchically:
- Each higher grade includes all lower grades plus new operations
- Each grade is defined by what operations become possible, not merely by addition of parts
The 3-4-5 Relationship #
Berquist notes: three souls, four grades of life, five genera of powers form the sides of a 3-4-5 right triangle (9 + 16 = 25). This is a mnemonic aid—the numbers are not arbitrary but reflect geometric harmony in the structure of living things.
Examples & Illustrations #
Plant Preference Language #
We say plants “like” sun or shade, illustrating that even vegetative powers exhibit a kind of ordering toward suitable conditions. This shows desire is not unique to sensation or intellection.
Immobile Animals #
Low forms of animal life (e.g., organisms affixed to the ocean floor) have sensation and touch but cannot move from place to place. Their food comes to them through water movement. This illustrates why sensation does not automatically bring locomotion.
Response to Stimuli #
When an organism with sensation (but no locomotion) is touched with a needle, it retracts as if in pain. This demonstrates that sensation necessarily brings appetite, yet does not require the power to move from place to place.
Questions Addressed #
Q: Why distinguish five powers if there are only three souls? #
A: Powers represent all possible operations of living things; souls are distinguished by how they fundamentally rise above matter. One of the five powers (appetite) always accompanies another and thus doesn’t create a new soul.
Q: Does appetite constitute a separate level of life? #
A: No. Appetite always accompanies knowing (sensation or intellection) and thus adds no new operational grade. An animal cannot have sensation without appetite, nor intellection without will.
Q: How do we reconcile the two/three-fold divisions with the five-fold division? #
A: Different principles of division are at work:
- Two-fold: Whether the power acts upon objects (vegetative, locomotive) or receives impressions from objects (sensitive, appetitive, intellectual)
- Three-fold: The three souls (vegetative, sensitive, rational)
- Five-fold: All specific genera of powers
When formally distinguishing powers, the five-fold division is correct.
Q: Why is desire common to all powers if appetite is a separate genus? #
A: The universal inclination of all powers toward their objects differs from appetitive power proper. Appetitive power is the desiring power that specifically follows upon sensation or intellection, not every power’s natural ordering toward its object.
Connections to Previous Material #
- Builds on the analysis of how we know the soul through its powers, powers through their acts, and acts through their objects
- Presumes familiarity with Aristotle’s De Anima Book II and Thomas’s commentary structure
- Relates to the doctrine of the separated soul: understanding and will remain, but sensitive and vegetative powers do not remain in act